Priority based methods and apparatus for transmitting accurate emergency location identification numbers (ELINs) from behind a multi-line telephone system (MLTS)

ABSTRACT

Methods for accurate transmission of ELIN/callback number from an emergency caller calling from behind a PBX/MLTS include prioritizing the emergency call, assigning a port equipment number to each device/trunk of the PBX/MLTS and associating ports/devices with ELINs and callback numbers. The apparatus of the invention detects an emergency number, assigns the call priority, and uses the port/device number to determine the ELIN/callback number and properly transmit the ELIN/callback number.

This application is related to co-owned co-pending application Ser. No.09/816,843 entitled “Methods And Apparatus For Transmitting AccurateEmergency Location Identification Numbers (ELINs) From Behind AMultiline Telephone System (MLTS) Utilizing Port Equipment Numbers”;co-owned co-pending application Ser. No. 09/816,830 entitled “MethodsAnd Apparatus For Transmitting Over A Private Network Accurate EmergencyLocation Identification Numbers (ELINs) From Behind A MultilineTelephone System (MLTS) Utilalizing Port Equipment Numbers”; co-ownedco-pending application Ser. No. 09/816,823 entitled “Methods AndApparatus For Transmitting Accurate Emergency Location IdentificationNumbers (ELINs) From Behind A Multi-Line Telephone System (MLTS) AfterAn Emergency Caller Disconnects”; co-owned co-pending application Ser.No. 09/816,838 entitled “Methods And Apparatus For Transmitting AccurateEmergency Location Identification Numbers (ELINs) After An EmergencyCaller Disconnects”; co-owned co-pending application Ser. No. 09/815,685entitled “Methods And Apparatus For Dialing An Emergency TelephoneNumber From A Teleworking Client Remotely Coupled to a PBX”; andco-owned co-pending application Ser. No. 09/815,468 entitled “System ForDialing An Emergency Telephone Number From A Teleworking Client RemotelyCoupled To A PBX”, the complete disclosures of which are herebyincorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to telecommunications systems, especiallyPBX/Server systems, also referred to as Multi-Line Telephone Systems(MLTS). Specifically, the invention relates to completing an emergency,e.g. 911, call from a station/device behind a MLTS to a public networkemergency facility and delivering precise location information of thecaller based on a port equipment number associated with the port fromwhich the emergency call originated.

2. Brief Description of the Prior Art

When a caller calls an emergency number, e.g. 911, the call is routed toa Public Safety Answering Point (PSAP). In some jurisdictions,regulatory agencies require that the caller's telephone number/callbacknumber and/or precise physical location referred to as LocationIdentification Number (ELIN), be automatically provided to the PSAP.This information is used to locate the caller and to call back to thecaller should there be a disconnect.

A caller identification (i.e., telephone number and ELIN) may bedelivered to the PSAP either in-band (e.g., using DTMF signaling) orout-of-band (e.g., using ISDN signaling) depending on the type of trunkcircuit employed. For residential callers Caller ID number is sufficientfor the PSAP. For PBX/server service many users, e.g., commercialcallers, hotel guests; an ELIN is required for this complex environment,for example, street address, floor number, room number, desk number. Insome cases, the ELIN is geodetic, i.e. includes earth coordinates or GPSdata.

Modern PBX/MLTS systems provide many new features to accommodate the waymodern businesses operate. For example, employees may be assignedpersonal identification numbers (PINs) that are used by the PBX/MLTS toidentify the employee and assign a telephone number to him/her. Further,for example, if an employee is assigned to a different location in thebuilding, an automatic relocation feature can be activated using the PINto reassign the employee's telephone number to the new location.

Another feature of PBX/MLTS systems is that some telephones connected tothe PBX/MLTS system may not be provided with the ability to receivedirect (inward) dialed calls. For example, in a hotel, telephones inrooms are typically not capable of receiving a direct inward call fromoutside the hotel, therefore they have no known Caller ID to identifythem to the PSAP. no known Caller ID to identify them to the PSAP.

Still another feature of modern PBX/MLTS systems is that it is possibleto make many or even all telephone lines available for use by multilinedevices connected to the system. Thus, a caller from behind the PBX/MLTSsystem may be identified by many different telephone numbers.

All of these features of modern PBX/MLTS systems present problems fortransmitting call back number and ELIN to a PSAP in an emergency call.In many situations, the only callback number provided from the PBX/MLTSsystem is the main directory billing number. In situations where thecaller has utilized the automatic relocation feature of the PBX/MLTSsystem, the caller will be identified by employee PIN but not by aspecific location. In situations where the caller has no direct inwardcall receive capability, the PSAP cannot call back the caller in theevent of a disconnect. In the situation of a call from a multilinedevice, the telephone number from which the emergency call is made maynot be the primary number for the caller and a return call to thatnumber may cause a different device to ring rather than the caller'sdevice. Moreover, the number used by the emergency caller may beassociated with a ELIN which is not the caller's ELIN.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide methods andapparatus for accurately reporting the ELIN of an emergency callerbehind a PBX/MLTS system to a PSAP.

It is also an object of the invention to provide methods and apparatusfor operating a PBX/MLTS system wherein emergency calls are givenpriority treatment over non-emergency calls (e.g., when al trunks busyconditions exists, first available trunk is awarded to an emergencycall); and to accurately report the callback number of an emergencycaller behind a PBX/MLTS system to a PSAP.

It is another object of the invention to provide methods and apparatusfor accurately reporting the ELIN and callback number of an emergencycaller behind a PBX/MLTS system to a PSAP that do not interfere with thefeatures of the PBX/MLTS.

It is yet another object of the invention to provide methods andapparatus for accurately reporting the ELIN and callback number of anemergency caller behind a PBX/MLTS system to a PSAP wherein thegranularity of ELIN can be determined by the administrator of thePBX/MLTS.

It is another object of the invention to provide methods and apparatusfor accurately reporting the ELIN of an emergency caller behind aPBX/MLTS system to a PSAP that includes identifying the type of ELIN,e.g. geodetic or non-geodetic.

It is still another object of the invention to provide methods andapparatus for managing a database of ELINs and callback numbersassociated with a PBX/MLTS system.

It is yet another object of the invention to provide methods andapparatus for accurately reporting the ELIN and callback number of anemergency caller behind a PBX/MLTS system to a PSAP wherein multipleemergency numbers are supported.

It is another object of the invention to provide methods and apparatusfor operating a PBX/MLTS system wherein emergency calls are givenpriority over non-emergency calls.

It is still another object of the invention to provide methods andapparatus for accurately reporting the ELIN and callback number of anemergency caller behind a PBX/MLTS system to a PSAP wherein the call isrouted over a private network before reaching the public network.

It is yet another object of the invention to provide methods andapparatus for accurately reporting the ELIN and callback number of anemergency caller behind a PBX/MLTS system to a PSAP using ISDN ornon-ISDN trunking facilities.

In accord with these objects which will be discussed in detail below,the methods according to the invention include assigning a portequipment number (PEN) to each port associated with the PBX/MLTS system,maintaining a database of ELIN and callback numbers associated withPENs, identifying an emergency number when it is dialed, invoking anemergency service routing upon detection of a dialed emergency number,associating the PEN with the dialer of the emergency number, retrievingthe ELIN and callback number (and optionally other information) from thedatabase, and transmitting the ELIN (according to PRI standards i.e.,Generic Information IE) and callback number to the PSAP.

The apparatus of the invention includes database management means,emergency number detection means, call routing means, ISDN and non-ISDNsignaling means. The invention may be configured so that either thecallback number, the ELIN, or both are transmitted to the PSAP. Further,the invention may be configured to recognize multiple emergency numbersand to give emergency calls priority over non-emergency calls.

The specificity of the ELIN can be determined by the systemadministrator and additional information may be associated with theELIN. The call routing and signaling means are capable of routing theemergency call through multiple PBX/MLTS systems before reaching thepublic network.

Additional benefits and features of the invention will be apparent fromthe following detailed description taken together with the attacheddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a high level illustration of a PBX/MLTS system according tothe invention in the process of making an emergency call;

FIG. 2 is a high level block diagram of the apparatus of the invention;

FIG. 3 is a high level block diagram of the call processor and devicehandler of FIG. 2;

FIG. 4 is a high level diagram of the database structure according tothe invention; and

FIG. 5 is a high level flow chart illustrating the methods of theinvention.

DETAILED DESCRIPTION

FIG. 1 provides by way of example an overview of an emergency call asoriginated in a private network (via MLTS 10) on Customer PremiseEquipment (CPE) 12.

According to the invention in the context of the aforementioned example,the call may be routed directly to the public network 14 or firsttransit over the private network (via one or more other MLTS 16) to afar end “hop off” to the public network 14. The private network routemay include ISDN (e.g., QSIG/PSS1) or analog tie trunks.

Furthermore, according to the invention, the ELIN/callback number issent with the emergency call over the private network 7 then to thepublic gateway MLTS 16. The encoding of the DTMF tones over analog tieand facility IE APDU are implementation dependent private extensions ona private network. The MLTS 10 or 16 may send the emergency call andELIN/callback number via an ISDN PRI or analog CAMA (centralizedautomatic message accounting) trunk to the public network 14. In eithercase, the central office 18 receives the information and routes the callto the proper 911 Tandem Office 20 which routes the call to theappropriate PSAP 22, 24.

A special Automatic Location Identification database (ALI DB) 26 ismaintained to match the received ELIN and/or Callback number and displayassociated information at the PSAP. It is the MLTS administrator'sresponsibility that the caller information be correctly listed in theALI DB.

Referring now to FIG. 2, an MLTS 10 according to the invention includesa database 30, a database administration module 32, a call processingmodule 34, a device handler 36, an emergency services (ES) module 38,and a dependability module 40. The dependability module 40 provides callrecovery functions in the event of an equipment failure.

According to the presently preferred embodiment, the trunk side of theMLTS 10 includes an ISDN Primary Rate Interface 42, a private ISDNinterface 44 for coupling to other customer equipment, and an analoginterface 46 for coupling to either the public network or the privatenetwork.

As mentioned hereinbefore, on the user/line side of the MLTS 10, eachuser equipment is coupled to a unique port and each port is assigned aunique port equipment number (PEN) 48. As described in more detail belowwith reference to FIG. 5, when an emergency call is dialed, callprocessing FIG. 2 34 recognizes the digits and invokes emergencyservices 38 which, using the PEN 48 retrieves the appropriateinformation from the database 30. The device handler 36 providesnecessary signaling/outpulsing depending on the type of trunk used. Theinvention doe not preclude the ability to assign incoming trunks (thatare emergency calls) with PENs to the ELIN database.

Referring to FIG. 3, the call processing module 34 includes a least costrouting (LCR) module 34 a, an invoke ES module 34 b, and a basic callprocessing module 34 c. The device handler 36 includes a privatesignaling module 36 a (e.g., analog tie DTMF, QSIG), a public signalingmodule (e.g., CAMA, primary rate interface (PRI)) 36 b through whichcalls are setup and ELIN/callback number data is transmitted via link 36c or 36 d.

When the emergency caller 48 dials (e.g., 911), a connect requestinternal message is sent to the call processing module 34. The emergencydigits are recognized by least cost routing (LCR) 34 a and emergencyservices (ES) 38 is invoked for this call.

According to the invention, the emergency digits are recognized at 34 bdepending on how the unit has been programmed. For example, an indicatoron one or more digit patterns in the dial plan flags this as anemergency call when the digits match.

This mechanism “triggers” ES processing 38. ES 38 performs all thenecessary functions to deliver this call as a priority emergency callwith correct ELIN and Callback Number to the basic call processor 34 c.Normal processing resumes for trunk selection, basic call establishmentsending an internal message with the ELIN and Callback Number to DeviceHandler 36.DH 36 formats the call information appropriately for thetrunk which has been awarded.

When the trunk is a private trunk 36 d, the ELIN and/or Callback Number(calling party number CPN) are formatted in a proprietary encoding. Whenthe trunk is a public trunk 36 c, the ELIN and Callback Number areformatted according to the trunk protocol required (e.g., CAMA, PRI).The trunk facilities may be non-ISDN with DTMF signaling or ISDN wherethe ELIN and Callback Number are encoded in the SETUP message (GenericInformation IE) sent on the signaling channel.

FIG. 4 is an example of the internal tables associated with the databaseof the invention. Table 1 50 is a PEN-to-ELIN index table and Table 2 52is a ELIN index-to-ELIN and callback number table.

Referring now to table 1 50, the first column 54 is a list of all PENswhich have a device/trunk that can originate an emergency call. Thesecond column 56 identifies all of the devices sharing the same PEN(e.g., multi-drop configuration) and the third column 58 provides anindex number to it's assigned ELIN/Callback entry for each device/trunk.The invention does not preclude or limit the usage of device or trunktypes (e.g., analog POTS, IP phone, workstation).

Typically, each PEN is associated with only one end device and thereforeassociated with only one ELIN index value shown in the third column.Therefore, the device column 56 is optional/not used. The ELIN indexvalue is a pointer into table 2. The system administrator assigns anindex to each PEN or device within a PEN (i.e., multi-drop).

The optional device column 56 may consist of several entries, eachassociated with that same PEN value. This allows for multiple enddevices to be configured and connected to one jack and therefore, onePEN. Each device specified has it's own associated ELIN index valuewhich may be different from another device on that same PEN. When ESretrieves an emergency call's PEN, when there is more than one enddevice, it must be able to identify which logical (or physical) deviceinitiated the call (i.e., 1–n) and use both the PEN and device number toselect the associated ELIN index.

Table 1 may be any length. The PEN field may optionally be set up torepresent a range of PENs rather than a single PEN. The format of thePEN is implementation-dependent. Optional fields may further identifythe PEN/device.

Table 2 52 is, for example, an indexed table where a list of the ELINindex numbers is represented in the first column 60, and the tableincludes a list of the associated ELINs in the second column 62, a ELINtype indicator in the third column 64, the callback number associatedwith the ELIN in the fourth column 66 at other optional fields such as,a text description of the ELIN in the fifth column 68, and a populationfield in the sixth column 70.

In this table example the ELIN index number obtained from table 1 isused to access the corresponding index value table entry in the firstcolumn of Table 2. This table entry provides the actual 10-digit NANP(North American Numbering Plan) ELIN assignment as seen in the secondcolumn. The invention does not preclude the usage of another type oftable access nor is limited with it's contents (e.g., otheridentification information).

The assignment of ELIN values are the responsibility of the CPEadministrator. The ELIN values are reported to the PSAP who should havea matching ELIN value in their ALI database with associated locationinformation.

The ELIN type indicator is applicable when a PRI connection to the PSAPis used. The ELIN type value correlates to the Generic InformationInformation Element (IE) octet 3 (bits 5 –1) Type of Information asdefined in the American National Standard T1.628-2000.

The two current defined values represent whether the informationadministered in the ELIN field is Geodetic or non-Geodetic information.The Callback# field 66 is a 10-digit NANP public network number whichcan be used by the PSAP to dial the caller back should the connection bebroken. The CPE administrator designates which phone number is to beused as the Callback Number associated with this ELIN, typically it'sDID number if available or a phone relatively close to the physicallocation of the calling location or possibly a receptionist.

Optional fields, such as the Description field 68 is a comments fieldused by the local administrator to help identify the ELIN. The POP (forpopulation) field 70 is an internal register which is incremented anddecremented each time a PEN is assigned/deassigned this table entryindex in the PEN-to-ELIN table via an administrative action. Therefore,it represents the number of PENs that are currently assigned to thisparticular ELIN and Callback Number. The content of Table 2 iscompletely flexible. ELINs and Callback Numbers can appear multipletimes in the table. The size of the table is implementation-dependent.

Tables 1 and 2 reside in each MLTS in a network. The ES processing andELIN/Callback Number retrieval occurs at the originating MLTS. Theresulting call information is transmitted either to the public networkor first over the private network for far end hop off to the publicnetwork. This does not preclude the destination of an emergency callbeing on-site with delivery of ELIN and Callback Number to a localemergency call operator. This may be desired when the organizationresponsible for the MLTS screens all emergency calls at a designatedcentral location or when the organization has its own emergencypersonnel such as security guards and medical personnel.

FIG. 5 is an example of a high level flow chart illustrating the logicof the processing of an emergency call according to the invention.Starting at 72, a station user dials an emergency number (e.g., 911).The LCR processes the digits at 74 and recognized the digits asrepresenting an emergency call at 76. LCR invokes ES at 78. ES (80–86)assigns the call priority at 80, retrieves the PEN/device number at 82,obtains ELIN index from table 1 at 84, and obtains ELIN, type andcallback number from table 2. ES turns over the information to thedevice handler which formats the information at 88 and proceeds withnormal call processing at 90.

Though not illustrated in FIG. 5, if a matching PEN cannot be found, theinvention may optionally report the missing PEN, exit ES, and continuewith regular call processing. If a matching PEN was found and no devicenumber applies, ES retrieves the ELIN index associated with this PEN. Ifa matching index is not found in table 2, the invention may optionallyreport the missing index and PEN, exit ES, and continue with regularcall processing.

There have been described and illustrated herein methods and apparatusfor precise reporting to a PSAP of an accurate ELIN/callback number froman emergency caller calling from behind a PBX/MLTS. While particularembodiments of the invention have been described, it is not intendedthat the invention be limited thereto, as it is intended that theinvention be as broad in scope as the art will allow and that thespecification be read likewise. It will therefore be appreciated bythose skilled in the art that yet other modifications could be made tothe provided invention without deviating from its spirit and scope as soclaimed.

1. A method for processing an emergency call made from behind a PBX/MLTScoupled to a private network, said method comprising the steps of: a)within the PBX/MLTS determining whether dialed digits represent anemergency number; b) assigning priority within the PBX/MLTS to a calldetermined to be an emergency call, such that said call takes priorityover other calls in traversing said private network before reaching apublic network trunk; c) storing a port equipment number for eachdevice/trunk in the PBX/MLTS; and d) associating a callback number witheach port equipment number.
 2. A method according to claim 1 furthercomprising the steps of: e) determining from which port the emergencycall originated; and f) transmitting to a public safety answering pointthe callback number associated with the port from which the emergencycall originated.
 3. A method according to claim 1 wherein said privatenetwork includes a second PBX/MLTS.
 4. A method according to claim 3further comprising the step of: c) processing said emergency call insaid private network based on said assigned priority.
 5. A method forprocessing an emergency call made from behind a PBX/IMLTS coupled to aprivate network, said method comprising the steps of: a) within thePBX/MLTS determining whether dialed digits represent an emergencynumber; b) assigning priority within the PBX/MLTS to a call determinedto be an emergency call, such that said call takes priority over othercalls in traversing said private network before reaching a publicnetwork trunk; c) storing a port equipment number for each device/trunkin the PBX/IMLTS; and d) associating an emergency locationidentification number (ELIN) and a callback number with each portequipment number.
 6. A method according to claim 5 further comprisingthe steps of: e) determining from which port the emergency calloriginated; and f) transmitting to a public safety answering point theELIN and the callback number associated with the port from which theemergency call originated.
 7. An apparatus for processing an emergencycall made from behind a PBX/MLTS coupled to a private network, saidapparatus comprising: a) means within the PBX/MLTS for determiningwhether dialed digits represent an emergency number; b) means forassigning priority within the PBX/MLTS to a call determined to be anemergency call, such that said call takes priority over other calls intraversing said private network before reaching a public network trunk;c) means for storing a port equipment number for each device/trunk inthe PBX/MLTS; and d) means for associating a callback number with eachport equipment number.
 8. An apparatus according to claim 7 furthercomprising: e) means for determining from which port the emergency calloriginated; and f) means for transmitting to a public safety answeringpoint the callback number associated with the port from which theemergency call originated.
 9. An apparatus according to claim 7 whereinsaid private network includes a second PBX/MLTS.
 10. An apparatus forProcessing an emergency call made from behind a PBX/MLTS coupled to aprivate network, said apparatus comprising: a) means within the PBX/MLTSfor determining whether dialed digits represent an emergency number; b)means for assigning priority within the PBX/MLTS to a call determined tobe an emergency call, such that said call takes priority over othercalls in traversing said private network before reaching a publicnetwork trunk; c) means for storing a port equipment number for eachdevice/port in the PBX/MLTS; and d) means for associating an emergencylocation identification number (ELIN) and a callback number with eachport equipment number.
 11. An apparatus according to claim 10 furthercomprising: e) means for determining from which port the emergency calloriginated; and f) means for transmitting to a public safety answeringpoint the ELIN and the callback number associated with the port fromwhich the emergency call originated.